In RF communications, there are instances especially within buildings and in connection with other structures such as walls or containers where these structures create a barrier to the transmission of the RF signals. Many illustrations of such RF shielding may be envisioned. However, two such scenarios will be described by way of illustration only.
First, the use of RF identification and wireless sensor technology is spreading in the supply chain and transportation industries. Goods equipped with RF tags and sensors are nested within larger containers for transport. Typical inter-modal cargo containers are constructed with steel that creates an RF barrier which limits access to the tags and sensors to the times when the containers are open, loaded, or unloaded. A solution that allows access to the tags and sensors from outside the container at any time is an attractive feature from both a logistics and a security standpoint. For all practical purposes, a metallic cabinet also acts as a RF shield for tagged items inside it. So, the term container used in this document is used to also refer to traditional metallic cabinets, or drawers.
Moreover, wireless services are often lost when a subscriber enters an elevator, since the elevator car creates an effective RF barrier. Improvements in the quality of service are always pursued by wireless service providers for competitive reasons, so a solution which offers uninterrupted access to in-building wireless services when a subscriber enters an elevator can be very compelling. Given the existing number of containers and elevators in use today, a low cost solution such as an improved passive repeater that is easily installed and does not require modification to the container or elevator is needed.